This invention relates to a light-sensitive silver halide photographic material for X-ray photography, having high diagnosis ability. More particularly, it relates to a light-sensitive silver halide photographic material for X-ray photography, having wide exposure latitude to make the material easy to use and capable of producing images of such high sharpness as to readily make the diagnosis.
In X-ray photographing of every parts of a living body by use of a light-sensitive silver halide photographic material for X-ray photography (hereinafter referred to merely as "X-ray sensitive material" including those to be classified into a material having light-sensitive emulsion layers on both sides of a substrate and a material having a light-sensitive emulsion layer on one side of a substrate), it is required for the X-ray sensitive material to have high diagnosis ability in order to make an early detection of a focus (a localized area of disease) and prevent erroneous diagnosis. However, conventional X-ray sensitive materials are not necessarily satisfactory to this effect.
Namely, in the conventional direct X-ray sensitive materials, which are roughly classified into a high gamma type represented by (a), a low gamma type represented by (b) and a middle type represented by (c) in the photographic characteristic curves shown in FIG. 1, respectively, the high gamma type (a) has high sharpness, but has too narrow exposure latitude to use easily; the low gamma type (b) has, on the contrary, so wide exposure latitude as to be easy to use, but has too low sharpness to make diagnosis; and the middle type (c) has only middling sharpness and middling exposure latitude.
When the direct X-ray sensitive materials of these types are processed by use of the same developer as used in this invention, typical examples of the gamma (Gamma-1) between optical densities of 0.50 and 1.50 and the gamma (Gamma-2) between optical densities of 2.00 and 3.00 on the photographic characteristic curve can be shown as in Table 1.
TABLE 1 ______________________________________ Gamma 1 Gamma 2 D = 0.50-1.50 D = 2.00-3.00 ______________________________________ High gamma type: 2.6 to 3.0 2.8 to 3.5 Middle type: 2.4 to 2.7 2.5 to 3.0 Low gamma type: 2.0 to 2.2 1.2 to 1.5 ______________________________________
In actual examples of the X-ray photography using these conventional types of the direct X-ray sensitive materials, even serious defects or incovenience such as follows have been caused: One of the living body parts of which X-ray photographs are most frequently taken is a the stomach, where a contrast medium is used in order to enhance the image depictivity. In the case of the conventional high gamma type direct X-ray sensitive material, where the exposure is adjusted to the contrast medium itself, no image other than entirely black image is obtained, after development, in respect of the part having no contrast medium. Thus, these materials have not been contributory at all to making any diagnosis. In order to prevent such a consequence, there have been frequently used low gamma type direct X-ray sensitive materials. In this case of this X-ray sensittive materials, however, the sharpness is lowered on the contrary and therefore the diagnosis ability decreases for the part of stomach wall containing the contrast medium. In another example for X-ray photographing of other parts of a living body, the X-ray photographs are taken of bones such as hands and legs and soft tissues such as flesh and cartilages. In these cases also, the conventional high gamma type X-ray sensitive materials may be useful for attaining high sharpness in respect of fine structures of bones, but may result in entirely black image in respect of soft tissues, and therefore have not been contributory to making the diagnosis. On the contrary, when the low gamma type X-ray sensitive materials are used, the soft tissues can be imaged, but the sharpness of images of bones are lowered.